Disjoining pressure and thinning transitions in smectic-<i>A</i>liquid crystal films

Picano, Frédéric; Oswald, P.; Kats, E. I.

doi:10.1103/physreve.63.021705

Cited by 56 publications

(90 citation statements)

References 22 publications

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“…Such a criterion is analogous to the nucleation condition of an elementary dislocation loop in self-supported smectic films, which exhibit thinning transitions qualitatively similar to those of confined OMCTS films [41,42]. Taking for Γ el the value determined above, we obtain a critical nucleation radius on the order of a few micrometers, considerably larger than the estimate made by Persson and Tosatti.…”

Section: Inward Frontssupporting

confidence: 53%

Drainage of a nanoconfined simple fluid: Rate effects on squeeze-out dynamics

Bureau

Arvengas

2008

Phys. Rev. E

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We investigate the effect of loading rate on drainage in molecularly thin films of a simple fluid made of quasi-spherical molecules (octamethylcyclotetrasiloxane, OMCTS). We find that (i) rapidly confined OMCTS retains its tendency to organize into layers parallel to the confining surfaces, and (ii) flow resistance in such layered films can be described by bulklike viscous forces if one accounts for the existence of one monolayer immobilized on each surfaces. The latter result is fully consistent with the recent work of Becker and Mugele, who reached a similar conclusion by analyzing the dynamics of squeeze-out fronts in OMCTS [T. Becker and F. Mugele, Phys. Rev. Lett. 91 166104 (2003)]. Furthermore, we show that the confinement rate controls the nature of the thinning transitions: layer-by-layer expulsion of molecules in metastable, slowly confined films proceeds by a nucleation/growth mechanism, whereas deeply and rapidly quenched films are unstable and undergo thinning transitions akin to spinodal decomposition.

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Section: Inward Frontssupporting

confidence: 53%

Drainage of a nanoconfined simple fluid: Rate effects on squeeze-out dynamics

Bureau

Arvengas

2008

Phys. Rev. E

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“…8 by 25%. We have no quantitative data for the contact angle in the present material, but this angle would be about one order of magnitude larger than available literature data [29,30] in smectic A. Moreover, such a large contact angle would be detectable in the catenoid profiles.…”

Section: Discussion and Summarymentioning

confidence: 45%

“…Such finite contact angles between meniscus and film have been measured quantitatively, e.g. [29,30]. This would result in a more effective surface reduction of the Plateau border by LC decoration, and consequently to an even lower effective line tension.…”

Section: Discussion and Summarymentioning

confidence: 99%

Plateau borders of smectic liquid crystalline films

Trittel

Aldred

Stannarius

2011

Philosophical Magazine

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“…Thus, as shown in Figs. 2 B and C and 4 A and B for events having N ¼ 2 islands on N ¼ 1 holes the island growth velocity v 21 is very close to half that of the hole shrinking velocity v 12 . This result implies that η 21 ¼ 2η 12 in Eq. 1, since the island and hole interface motion are driven by the same δP and Δu.…”

Section: Resultsmentioning

confidence: 80%

“…By contrast, the freely suspended monolayer, having air on both sides so that end-to-end flips are energetically equivalent, is describable as a zero field 2D Ising system, with the in-plane interactions determining the states and size of the domains of common σ (11). Another source of difference in the surface free energy between monolayer and multilayer films is the disjoining pressure resulting from several effects due to the proximity of the film's two surfaces (12).…”

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confidence: 99%

Surface energetics of freely suspended fluid molecular monolayer and multilayer smectic liquid crystal films

Nguyen

Park

Pang

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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A study of the surface energetics of the thinnest substrate-free liquid films, fluid molecular monolayer and multilayer smectic liquid crystal films suspended in air, is reported. In films having monolayer and multilayer domains, the monolayer areas contract, contrary to predictions from the van der Waals disjoining pressure of thin uniform slabs. This discrepancy is accounted for by modeling the environmental asymmetry of the surface layers in multilayer films, leading to the possibility that preferential end-for-end polar ordering of the rod shaped molecules can reduce the surface energy of multilayers relative to that of the monolayer, which is inherently symmetric.fluid film | liquid crystals T he attractive Van der Waals interaction makes it possible for the existence of the liquid phase, which, at a temperature lower than the critical temperature, can coexist and share an interface with a gas phase that has different structure and properties (1). At this interface, the density changes across a distance on the order of the intermolecular distance of the liquid, resulting in a difference between the tangential stress and the normal pressure which generates the surface tension, equal to the excess surface energy (2, 3). It is thus interesting to study the surface energetics and tension in ultra-thin films in which the density and the normal pressure inside the liquid are not those of the bulk. These differences become larger as film thickness becomes smaller, so ultrathin films are of interest. However, liquid films in air thinner than h ≈ 2.5 nm rupture via spontaneous pore formation due to surface tension (4). Thus, in order to be stable against rupture, films must be internally structured to suppress thinning and maintain h ≥ 2.5 nm.Fluid smectic liquid crystals (LCs) are three dimensional (3D) phases of rod shaped molecules organized into periodic stackings of molecular layers, where each layer is a 2D liquid. At the air/LC interface, the smectic layering exhibits a strong tendency for the layers to be parallel to the interface, and thus for the molecules at the interface to be in the same smectic layer, typically of thickness d ≈ 3 nm. This organization enables the formation and stabilization of freely suspended smectic films consisting of an integral number, N, of smectic layers, where, for some materials, N can be as small as N ¼ 1, that is, fluid monolayers stable for extended periods have been made in several different materials (5,6,7,8). These fluid films are unique among monolayer liquid systems in that they are in a symmetric environment with vapor on both sides. Such substrate-free monolayer fluid molecular films are of fundamental interest in soft matter nanoscience, serving as fluid systems of reduced dimensionality for the study of fluctuation, symmetry, and interface effects (9, 10). Here we show that single and few layer smectic films can be used to measure the surface energy of a substrate-free fluid molecular monolayer.In smectic layers, the molecular long axes are narrowly distributed in...

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Disjoining pressure and thinning transitions in smectic-Aliquid crystal films

Cited by 56 publications

References 22 publications

Drainage of a nanoconfined simple fluid: Rate effects on squeeze-out dynamics

Drainage of a nanoconfined simple fluid: Rate effects on squeeze-out dynamics

Plateau borders of smectic liquid crystalline films

Surface energetics of freely suspended fluid molecular monolayer and multilayer smectic liquid crystal films

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